Identification of viable myocardium by perfusion imaging with intravenous contrast echocardiography after acute myocardial infarction

Myocardial perfusion contrast echocardiography is evolving into an effective method for the evaluation of myocardial blood flow after acute coronary events. The direct injection of ultrasound contrast agents into the aortic and coronary circulation has been shown to accurately identify areas of viable myocardial tissue. Recently, intravenous ultrasound contrast has been found to be useful in detecting microvascular blood flow after the restoration of blood flow in patients with myocardial infarction. We present the case of a patient in whom intravenous ultrasound contrast assisted in the detection of viable myocardial tissue after an acute ischemic syndrome.     

Usefulness of myocardial contrast echocardiography early after acute myocardial infarction

OBJECTIVES: (1) Evaluate wall motion and perfusion abnormalities after reperfusion therapy of the culprit lesion, (2) delineate the ability of myocardial contrast echocardiography (MCE) to evaluate the microvasculature after reperfusion, in order to distinguish between stunning and necrosis in the risk area. METHODS: We analyzed 446 segments from 28 patients, 10 normal controls (160 segments), and 18 with a first AMI (286 segments). MCE was obtained with Optison and a two-dimensional echocardiography was performed at 3 months post acute myocardial infarction (AMI). RESULTS: In the group with AMI, we analyzed 286 segments, of which 107 had wall motion abnormalities (WMA) related to the culprit artery. Two subgroups were identified: Group I with WMA and normal perfusion (50 segments, 47%) and Group II with WMA and perfusion defects (57 segments, 53%). According to the 2D echocardiogram at 3 months, they were further subdivided into: Group IA: with wall motion improvement (stunning): 18 segments, 36%, Group IB: without wall motion improvement: 32 segments, 64%, Group IIA: with wall motion improvement: 12 segments, 21%, Group IIB: without wall motion improvement (necrosis): 45 segments, 79%. CONCLUSIONS: (1) The presence of myocardial perfusion in segments with WMA immediately after AMI reperfusion therapy predicts viability in most patients. Conversely, the lack of perfusion is not an absolute indicator of the presence of necrosis. (2) Perfusion defects allow to detect patients with thrombolysis in myocardial infarction (TIMI) 3 flow and "no-reflow" phenomenon who will not show improved wall motion in the 2D echocardiogram. However, some patients with initial no-reflow could have microvascular stunning and their regional contractile function will normalize after a recovery period.     

Myocardial contrast echocardiography in acute myocardial infarction

PURPOSE OF REVIEW: Myocardial contrast echocardiography (MCE) has evolved into an important clinical tool for imaging coronary microcirculation. It can be used to delineate the spectrum of perfusion derangements that characterize acute myocardial infarction. RECENT FINDINGS: Presently, MCE uses microcirculatory perfusion as the basis to distinguish myocardial necrosis and viability in the post-infarct stage. Its future role may expand to image cellular integrity, inflammation, and angiogenesis, all of which contribute to the pathophysiology of the myocardial infarction. SUMMARY: This review provides an update of the current role and future clinical applications of MCE in acute myocardial infarction.     

Myocardial contrast echocardiography is superior to other known modalities for assessing myocardial reperfusion after acute myocardial infarction

Background: Angiographic flow measurements do not define perfusion accurately at a microvascular level, so other techniques which assess flow at a tissue level are to be preferred.     

Identification of viable myocardium early after acute myocardial infarction using closed-loop arbutamine echocardiography: comparison with positron emission tomography.

OBJECTIVE: This study sought to evaluate the safety and efficacy of arbutamine echocardiography in identifying contractile reserve and predicting functional improvement early after acute myocardial infarction (AMI). METHODS AND RESULTS: Seventeen patients with first AMI underwent arbutamine echocardiography 48 to 96 hours after AMI. Arbutamine was infused by a closed-loop delivery device.The heart rate slope was 4 beats/min and the heart rate target was 20 beats/min above baseline heart rate. A follow-up echocardiogram was obtained one month later. N-13 ammonia and F-18 FDG positron emission tomographic (PET) imaging were performed 6 +/- 2 days after AMI, before coronary angiography. Mean duration of arbutamine infusion was 6 +/- 2 min.There was no complication and there were no major side effects. Myocardial viability was identified with PET in 15 of the 17 patients. Contractile reserve was observed in 10 patients during arbutamine infusion. Functional recovery was identified in 12 patients. Sensitivity, specificity and accuracy of PET and arbutamine echocardiography for predicting functional recovery were 100%, 40%, 76% and 67%, 80%, 84%, respectively. CONCLUSIONS: Low-dose arbutamine stress testing is safe early after AMI. Contractile reserve can be rapidly identified by echocardiography and is specific, but moderately sensitive for predicting reversible dysfunction.     

Detection of viable myocardium by transvenous myocardial contrast echocardiography using harmonic power Doppler: canine model of acute coronary occlusion and reperfusion

STUDY OBJECTIVE: To assess whether myocardial contrast echocardiography (MCE) using harmonic power Doppler (HPD) in conjunction with the transvenous contrast agent SHU 563A would be useful in detecting stunned but viable myocardium. DESIGN: Acute coronary occlusion (2 to 3 h) followed by 1 h of reperfusion was created in 10 dogs in an open-chest model. Measurements and results: Continuous harmonic B-mode for wall motion analysis and ECG triggered HPD for assessment of myocardial perfusion was employed during coronary occlusion and after reperfusion. Postmortem 2,3,5-triphenyltetrazolium chloride (TTC) staining was performed to verify infarction. Extent of wall motion abnormality (WMA), perfusion defect size, and anatomic infarct size (myocardial infarction [MI]) were analyzed in a 5-segment model. All 10 dogs showed WMA in 23 of 50 segments during coronary occlusion. In eight dogs, HPD detected perfusion defects in 18 of 50 segments. The concordance rate between WMA and perfusion defect was 86%. Mean linearized power (MLP) in segments with WMA was significantly lower compared to normal segments (60.7 +/- 38.9 vs 110.5 +/- 108.8, p < 0.05). After reperfusion, the extent of WMA was larger than the area of perfusion defect (percentage of left ventricular slice area): 30 +/- 13% vs 9 +/- 8%, p < 0.01. Eventual infarct size was 6 +/- 7%. WMAs were seen in 18 of 50 segments. TTC confirmed MI in 7 of 18 segments. MLP in segments with WMA but no MI was significantly higher compared to segments with WMA and MI (84.5 +/- 67.3 vs 13.2 +/- 9.6, p < 0.01). Thus, the extent of WMA after reperfusion was greater than the size of perfusion defect and eventual MI, indicating the presence of stunned but viable myocardium. CONCLUSION: MCE using HPD and the contrast agent SHU 563A can demonstrate the efficacy of reperfusion, identify necrotic regions, and aid in the recognition of stunned but viable myocardium. This approach could be useful clinically in patients with acute MI undergoing reperfusion therapy.     

Intracardiac measurement of pre-ejection myocardial velocities estimates the transmural extent of viable myocardium early after reperfusion in acute myocardial infarction.

OBJECTIVES: We hypothesized that wall motion velocity during pre-ejection is proportional to the regional content of viable myocardium after reperfusion for acute myocardial infarction (AMI). BACKGROUND: Pre-ejection wall motion consists of short and fast inward and outward movement towards and away from the center of the left ventricle (LV) and is altered during regional ischemia. This short-lived event can be accurately quantified by Doppler myocardial imaging (DMI). METHODS: Fourteen open-chest pigs underwent 60 to 120 min of left anterior descending coronary artery occlusion followed by 30 min of reperfusion. The DMI data were collected using a phased-array intracardiac catheter (LV cavity) from ischemic and nonischemic myocardium encompassed within a plane passing through two epicardial bead markers. Peak tissue velocities during isovolumic contraction (IVC) (peak positive and peak negative), ejection (S) and early filling (E) were measured. The cardiac specimen was sliced through the epicardial markers in a plane approximating the ultrasound imaging plane. The transmural extent of necrosis (TEN) (%) was measured by triphenyltetrazolium chloride staining. RESULTS: During ischemia, positive IVC velocity was zero in ischemic walls with TEN >20%. At reperfusion, positive IVC velocity correlated better with TEN (r = -0.94, p < 0.0001) than it did S (r = -0.70, p < 0.01) and E (r = -0.81, p < 0.01). Differential IVC (the difference between peak positive and peak negative velocity) highly correlated with TEN, during ischemia (r = -0.78, p < 0.001) and during reperfusion (r = -0.93, p < 0.0001). CONCLUSIONS: Pre-ejection tissue velocity, as measured by intracardiac ultrasound, allows rapid estimation of the transmural extent of viable myocardium after reperfusion for AMI.     

Usefulness of power Doppler contrast echocardiography to identify reperfusion after acute myocardial infarction

Microvascular integrity, as seen by myocardial contrast echocardiography (MCE), assesses whether myocardium has been successfully reperfused after an acute myocardial infarction. Until now this has been demonstrated only with intracoronary injection of an ultrasound contrast agent. Power Doppler imaging is a recently developed myocardial contrast echocardiographic method that counts the contrast microbubbles destroyed by ultrasounds and displays this number in color. This study sought to evaluate whether power Doppler MCE is able to visualize myocardial reperfusion during intravenous contrast injection. Thirty patients were evaluated 2 days after their first myocardial infarction during intravenous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA). Coronary artery angiography and single-photon emission computed tomography (SPECT) were used as reference techniques. A 16-segment left ventricular model was used to relate perfusion to coronary artery territories. Sensitivity and specificity of power Doppler MCE for segments supplied by infarct-related arteries were 82% and 95%, respectively. Accuracy of power Doppler MCE and SPECT were similar (90% vs 92% on segmental basis and 98% vs 98% on coronary artery territory basis). Two-dimensional echocardiography was repeated after 6 weeks. Segments recovering wall motion after 6 weeks were defined as stunning myocardium. Dysfunctional but perfused myocardium at day 2 after the infarction showed a better late recovery of wall motion compared with dysfunctional but nonperfused myocardium (p <0.001). In conclusion, harmonic power Doppler imaging is a sensitive and specific method for the identification of myocardial reperfusion early after myocardial infarction. It yields prognostic information for late recovery of ventricular function differentiating stunning (dysfunctional but perfused) from necrotic myocardium (dysfunctional and nonperfused).     

静息与负荷心肌造影超声心动图识别存活心肌的对比研究

目的探讨负荷心肌造影超声心动图(MCSE)对心肌梗死后存活心肌评价的疗效和安全性。方法选择冠状动脉造影证实的心肌梗死患者30例。首先在静息状态下行心肌造影超声心动图(MCE),MCE心肌灌注结果采用半定量评价。多巴酚丁胺负荷静脉滴注剂量分别为5、10、20μg·kg~(-1)·min~(-1),每期3 min观察心率、血压变化于达到负荷剂量后再次行MCE,并以~(18)F-脱氧葡萄糖正电子发射计算机体层扫描(PET)作为金标准评价其敏感性和特异性。结果 MCE总共评价360个梗死节段,静息MCE评价1、0.5、0分为264、22、74个节段。多巴酚丁胺负荷MCSE评价1、0.5、0分为286、30、44个节段,评价MCE敏感性和特异性分别为38.10%、88.89%,kappa=0.285(P0.01)。评价MCSE敏感性和特异性分别为86.21%、88.89%,kappa=0.746(P0.05)。结论MCE及MCSE安全性良好。MCE及MCSE均与冠状动脉造影心肌梗死部位有较好的相关性,以PET作为金标准,MCSE具有较高的敏感性和特异性,是评价梗死节段内存活心肌的较好方法。     

Assessment of myocardial blood flow and volume using myocardial contrast echocardiography

The development of new microbubble agents and ultrasound imaging modalities now allows the assessment of myocardial perfusion with echocardiography. Microbubbles also can be administered intravenously as constant infusions, which allows their concentration in blood to reach steady state. If the relation between microbubble concentration and video intensity is within the linear range, then myocardial video intensity will reflect the concentration of microbubbles in that region, which at steady state is the myocardial blood volume. The ability to destroy microbubbles and measure their replenishment into the ultrasound beam provides an opportunity to evaluate microbubble (or red blood cell) velocity. The product of myocardial blood volume and red blood cell velocity represents myocardial blood flow.     

Myocardial contrast echocardiography in acute myocardial infarction: Pathophysiological background and clinical applications

Myocardial contrast echocardiography is a technique used inexperimental and clinical settings in order to visualize thepattern of intramyocardial perfusion. In the acute phase ofmyocardial infarction, regional absence of flow during myocardialcontrast echocardiography delineates the area at risk of necrosis,while the definitive non-perfused area expresses infarct size.Reopening the infarct-related artery, which may be achievedspontaneously by thrombolysis or percutaneous transluminal coronaryangioplasty, is not a reliable indicator of intramyocardialreperfusion. If myocardial ischaemia due to coronary occlusionhas been sufficiently prolonged and severe, not only myocyteviability, but also microvascular integrity is lost. Myocardialcontrast echocardiography, using intracoronary injection ofsonicated contrast medium, gives information about microvascularintegrity and the effective presence of intramyocardial reflow.Anatomical integrity of microvasculature does not necessarilyimply preserved function, and thus the microvessel vasodilatingreserve may also be impaired. Myocardial contrast echocardiographyhas the potential to assess alterations in microvascular function,showing, in the myocardial area with reduced coronary reserve,a relatively reduced increase in echocontrast signal intensitywhen an intravenous vasodilator agent is administered. (Eur Heart J 1996; 17: 344–353)     

Incremental value of myocardial contrast echocardiography for the prediction of recovery of function in dobutamine nonresponsive myocardium early after acute myocardial infarction

We hypothesized that the presence of microvascular integrity, detected by myocardial contrast echocardiography (MCE) in dobutamine nonresponsive segments, may enhance identification of recovery of function, which is a surrogate marker of myocardial viability. Accordingly, 96 patients underwent dobutamine echocardiography (DE) and intravenous MCE on the same day, 4.6 +/- 1.5 days after acute myocardial infarction (AMI). Recovery of function of akinetic segments was assessed at 3 months after AMI. Of 387 akinetic segments, 102 (26%) recovered function during follow-up. Sensitivities and specificities of MCE, DE, and the combination of DE and MCE in dobutamine nonresponsive segments were 58%, 59%, and 79%, respectively (p <0.001, compared with MCE and DE) and 76%, 84%, and 69%, respectively (p <0.05 compared with DE) for predicting recovery of function. In anterior AMI, the positive and negative predictive values of MCE, DE, and the combination of DE and MCE were 47% and 88%, 57% and 89%, and 49% and 95%, respectively. Multivariate analysis using clinical characteristics, electrocardiography, biochemical factors, MCE, and DE showed that the combination of DE and MCE in dobutamine nonresponsive segments (p <0.00001) and Q-wave AMI (p = 0.002) were the only independent predictors of recovery of function. Thus, for optimum prediction of recovery of function after AMI, a combination of DE and MCE in dobutamine nonresponsive segments may be utilized.     

Prognostic value of myocardial viability detected by myocardial contrast echocardiography early after acute myocardial infarction.

OBJECTIVES: This study sought to determine whether residual myocardial viability determined by myocardial contrast echocardiography (MCE) after acute myocardial infarction (AMI) can predict hard cardiac events. BACKGROUND: Myocardial viability detected by MCE has been shown to predict recovery of left ventricular (LV) function in patients with AMI. However, to date no study has shown its value in predicting major adverse outcomes in AMI patients after thrombolysis. METHODS: Accordingly, 99 stable patients underwent low-power MCE at 7 +/- 2 days after AMI. Contrast defect index (CDI) was obtained by adding contrast scores (1 = homogenous; 2 = reduced; 3 = minimal/absent opacification) in all 16 LV segments divided by 16. At discharge, 65 (68%) patients had either undergone or were scheduled for revascularization independent of the MCE result. The patients were subsequently followed up for cardiac death and nonfatal AMI. RESULTS: Of the 99 patients, 95 were available for follow-up. Of these, 86 (87%) underwent thrombolysis. During the follow-up time of 46 +/- 16 months, there were 15 (16%) events (8 cardiac deaths and 7 nonfatal AMIs). Among the clinical, biochemical, electrocardiographic, echocardiographic, and coronary arteriographic markers of prognosis, the extent of residual myocardial viability was an independent predictor of cardiac death (p = 0.01) and cardiac death or AMI (p = 0.002). A CDI of < or = 1.86 and < or = 1.67 predicted survival and survival or absence of recurrent AMI in 99% and 95% of the patients, respectively. CONCLUSIONS: The extent of residual myocardial viability predicted by MCE is a powerful independent predictor of hard cardiac events in patients after AMI.     

Enhanced tolerance of the rat myocardium to ischemia and reperfusion injury early after acute myocardial infarction

It is now recognized that changes occurring during cardiac remodeling may influence the tolerance of the myocardium to ischemic stress. Therefore, the present study investigated the response of the post-infarcted heart to ischemia in an experimental model of ischemia and reperfusion injury and the possible underlying mechanisms. Acute myocardial infarction (AMI) was induced in Wistar male rats by ligating the left coronary artery (AMI, n = 13), while sham-operated rats were used as controls (SHAM, n = 11). At 2 weeks, cardiac dysfunction was observed in AMI, as indicated by the reduction of the left ventricular EF%. Isolated hearts were then subjected to 30 min of zero-flow global ischemia followed by 45 min of reperfusion. Ischemic contracture was significantly depressed in AMI hearts. Postischemic left ventricular end diastolic pressure (LVEDP45) in mmHg and LDH release in IU/g were markedly decreased; LVEDP45 was 52.1 (7.5) for AMI vs 96.6 (7.5),P < 0.05 and LDH release was 7.5 (1.0) in AMI vs 11.4 (0.56) in SHAM, P < 0.05. This response was associated with 2-fold increase in HSP70 expression in AMI hearts (noninfarcted segment), P < 0.05 vs SHAM and 1.7 fold increase in the expression of the phospho-HSP27, P < 0.05, while the expression of PKCε was shown to be 1.4-fold less in AMI, P < 0.05. In conclusion, the post-infarcted heart seems to be resistant to ischemiareperfusion injury and heat shock protein 70 and 27 may be involved in this response.     

Optimal time for predicting myocardial viability after successful primary angioplasty in acute myocardial infarction: a study using myocardial contrast echocardiography

This study sought to elucidate serial changes in microvascular integrity during papaverine-induced hyperemia in the risk area for myocardial infarction. In addition, we attempted to determine the optimal time for predicting myocardial viability. Seventy-two patients who underwent serial myocardial contrast echocardiography (MCE) before and shortly after (day 1), 1 day (day 2), and 3 weeks (day 21) after recanalization were studied. In 18 of 72 patients, MCE was performed at baseline and during hyperemia using selective intracoronary infusion of papaverine. Both the peak grayscale ratio (PGSR) within the risk area, and the no- and low-reflow ratio (LR ratio) were analyzed in each stage. Left ventricular regional wall motion (RWM) was determined 6 months after recanalization. The correlation coefficient between PGSR with papaverine on day 1 and that on day 2 was 0.54 (p = 0.02); it was 0.50 (p = 0.04) between day 1 and day 21, and 0.82 (p = 0.001) between day 2 and day 21. On day 1, the correlation coefficient between the LR ratio with papaverine and RWM was 0.60 (p = 0.02), which changed to 0.72 (p = 0.003) on day 2 and 0.54 (p = 0.04) on day 21, respectively. The best time to predict viable myocardium was established on day 2 by receiver operating characteristics curves. ST-segment re-elevation, elapsed time from onset to recanalization, and antecedent angina pectoris were independent factors for PGSR on day 2 using stepwise and multiple linear regression analysis. This study suggests that the optimal time to estimate microvascular integrity for predicting myocardial viability might be 1 day after recanalization, which is neither shortly after recanalization nor during the convalescent stage.     

Significance of early two-dimensional echocardiography after acute myocardial infarction

We performed serial two-dimensional echocardiography (2D echo) in 35 patients with a first transmural myocardial infarction, to correlate initial left ventricular wall motion abnormalities with subsequent in-hospital cardiac complications, peak total creatine kinase level, and haemodynamic alterations, and to observe serial changes in the left ventricular wall motion. A wall motion score was derived by analysing endocardial motion in 15 left ventricular segments. Left ventricular wall motion could be analysed in 30 patients, 14 without (Group 1) and 16 with complications (Group 2). The initial wall motion score in Group 1 patients was 5.2 +/- 0.7 (+/- SEM) compared to 14.2 +/- 1.2 in Group 2 patients (P less than 0.001). A wall motion score of greater than or equal to 10 correlated with the occurrence of complications in 15 of 16 patients (sensitivity 93%, specificity 92%). Initial wall motion score did not correlate significantly with peak total serum creatine kinase and did not change significantly during the first 72 hr in both the groups. In 12 patients who underwent right heart catheterization together with 2D echo, the average wall motion score was 16.4 +/- 2.0 and cardiac index 2.4 +/- 0.3. Wall motion score correlated inversely with the cardiac index in these patients (r = -0.78; P less than 0.01). Thus, 2D echo performed in first transmural myocardial infarction patients soon after admission can identify those likely to have in-hospital complications. 2D echo wall motion score correlated significantly with the cardiac output in this study.